Fault annunciator



July 25, 1961 PELQVITZ 2,994,073

FAULT ANNUNCIATOR Filed Feb. 5, 1958 e 6 I 92 39f39g,

INVENTOR'. MILTON PELOVITZ United States Patent 2,994,073 FAULTANNUNCIATOR Milton Pelovitz, 331 Williams St., Somerville, NJ. FiledFeb. 5, 1958, Ser. No. 713,362 2 Claims. (Cl. 340-213 This inventionrelates to an annunciator system, and more particularly to a faultannunciator that provides one or more indications of the occurrence ofan abnormal condition at any or all of a plurality of stations.

There are many instances where it is desirable to alert personnel of achange from a normal to an abnormal operating condition of machinery,other equipment, control systems, etc. This is particularly tnue whereautomatic equipment is used, for one of the advantages of automation isthat of minimizing personnel. Since automatic equipment functions forthe most part without attention, a minimum number of workmen can takecare of many machines. This creates a special problem, however, for theabsence of personnel in constant attendance to each piece of equipmentrequires that some means be employed to make known the occurrence ofmalfunctioning or other abnormal conditions.

As a consequence, annunciator or alarm systems have been developed foruse with automatic equipment, and such systems are operative to providevisual and audible indications whenever abnormal conditions are presentin the equipment. Known annunciator systems have been, for the mostpart, custom-made to accommodate particular conditions in giveninstallations and have been complex and quite expensive. There existsthen a need for a fault annunciator system that is simple in design andrelatively inexpensive, and that can be made to accommodate a largevariety of different equipment installations. It is, accordingly, ageneral object of this invention to provide a new and improvedannunciator system which is simple to construct and install, whichrequires a minimum of maintenance, which comprises components that areeconomical and of small size, and in which the amount of necessarywiring is minimized.

Another object of the invention is that of providing an annunci-atorsystem which employs a minimum of moving parts, and in which the remotecomponents of the system need not be sealed or otherwise protectedagainst the effects of dust, contamination, corrosive atmospheres, etc.

Still another object of the invention is that of providing anannunciator system in which there are no relays nor other components,with the exception of a fault switch, at the detecting stations.

A further object of the present invention is to provide an improvedannunciator system in which a single silenceable indication device isoperative in response to the occurrence of an abnormal condition at anyone of a number of detecting stations and which, subsequent to providingan indication of such abnormality at any one station, may be placed inreadiness to indicate an abnormality at another station even though thefirst faulty condition still persists.

Yet a further object is to provide a fault annunciator that employs aDC. current pulse to supply a threshold current of greater magnitude forenergizing a utilization device which controls an audible signal.

Additional objects and advantages of the invention will become apparentas the specification develops.

In accordance with the present invention, a unidirectional currentconductive switch in the form of a transistor is made operative inresponse to the closing of a Patented July 25, 1961 trouble or faultsensing switch which may be located at a detecting station, and in turnprovides a current flow sufficient to energize a utilization devicewhich may comprise a relay and controls the initiation of an audiblesignal. The transistor is made operative by the DC. current pulse thatappears when the trouble sensing switch is closed, and amplifies suchpulse to a threshold value sufiicient to energize the relay. Terminationof the DC pulse will not again energize the relay because of the unidirectional current flow characteristics of the transistor.

An illustrative embodiment of the invention is shown in the accompanyingdrawing, in which the single figure thereof is a schematic circuitdiagram of an annunciator system incorporating the present invention.

The fault annunciator, which is designated in its entirety with thenumeral 10, operates on a direct current power source which isexemplified in the drawing by a battery denoted with the numeral 11. Forconvenience, the positive and negative lines leading from the powersource 11 are designated, respectively, with the numerals 12 and 13.Preferably, the power source 111 has an output of from 18 to 24 volts,but it will be apparent that the value may be varied in accordance withthe requirements of the circuit components selected for use therewith.

Connected across the source 11 is a utilization device such as a relay14, one side of the energizing coil thereof being connected to thenegative line 13 through a lead 15. The opposite side of the energizingcoil is connected directly to the fixed contact 16 of the relay switch17, and also to a transistor or unidirectional impedance device 18through lead 19. The switch 17 defines a self-holding circuit for therelay 14, and the movable blade or contact 20 thereof is connected tothe positive line 12 through lead 21 which has a normally closedacknowledgment switch 22 interposed therein. It will be apparent thatthe relay 14 when once energized to close the switch 17 thereof, remainsenergized until the acknowledgment switch 22 is opened-assuming that atthe time the switch 22 is opened, the circuit through lead 19 isinterrupted, The switch 22 will be located at a convenient position, andordinarily will be manually operable.

A second relay switch 23 is also provided, and the normally open movablecontact 24 thereof is connected through lead 25 to the negative side ofthe power source 11. The fixed contact 26 of relay switch 23 isconnected to the positive side of the power source through a lead 27which has a signal device 28 interposed therein. The device 28 providesan audible signal alarm and may be a bell, as shown. When the relay 14is energized, the switch 23 thereof will be closed and the audiblesignal device 28 actuated, and this actuated state of the signal devicewill be maintained for as long as the relay is energized.

The transistor 18 has a base 29, an emitter 30 and collector 31, anddefines a uni-directional current conductive switch. The collector 31 isconnected to lead 19 and is, consequently, in series with the energizingcoil of the relay 14. The emitter 30 is connected directly to thepositive side of the power source 11 through lead 32, and it is apparentthen that the transistor is. in shunt connection with the self-holdingcircuit of the relay. The base 29 of the transistor is connected throughlead 33 to one side of the secondary winding 34 of a transformer 35. Theother side of the winding 34 is connected to the positive side of thepower source 11. The primary winding 36 of the transformer has one sidethereof connected to the positive terminal of the power source, and theother side thereof connected through lead 37 to one side of a pluralityof signal devices 38, 38a, 38b and 380 arranged in parallel with eachother. The signal devices 38 are intended to provide visual indicationsand may be in the form of lights, as shown.

Connected in series with the respective lights are fault sensingswitches 39, 39a, 39b and 39c, and each of these switches is in turnconnected to the negative side of the power source 11 through line 13.The fault sensing switches may be of any suitable type, such as pressureswitches, level controls, temperature controls, etc.; and are responsiveto a change in condition at a detecting station. Ordinarily, theseswitches are normally open, and will be closed in response to theoccurrence of an abnormal operating condition in a policed machine asthe same is reflected at the detecting station. It will be appreciatedthat each of the sensing switches defines a separate detection circuit;and thus, in the illustration, four separate detection circuits areshown. A lesser or greater number of detection arrangements may beemployed, depending upon the particular requirements of any giveninstallation.

Normally, the circuit will be in the condition shown in the drawing, andsuch condition will be maintained until a fault or change from normaloccurs in a piece of equipment or system, etc. policed by the circuit.In this normal condition, no current is flowing through the primarywinding 36 of the transformer for all of the fault sensing switches 39are open. The transistor 18 is biased at or near cut-off, and as aconsequence the relay 14 is de energized and the switches 17 and 23thereof are in their normally open state. Therefore, the visual signaldevices 38 and the audible signal device 28 are at rest.

If one of the fault sensing switches, 390 for example, is closed by achange from normality at a detecting station, current will flow throughthe primary winding 36 of the transformer and through the light 38c,thereby providing a visual indication of such variation in condition.The initiation of a D.C. current flow through the primary winding 36will induce a current flow in the secondary winding 34 of thetransformer, whereupon such transient current will make the transistor18 conductive. The armplification characteristics of the transistor willthereby establish a current flow through the energizing coil of therelay 14 of suflicient magnitude to energize the relay, whereupon theswitches 17 and 23 will be closed. Thereafter, the relay remains in itsenergized state because of the self-holding circuit defined through theswitch 17 thereof. As a result, an audible signal device 28 is actuatedthrough the relay switch 23. Since the flow of current through theprimary winding 36 of the transformer is of constant value (that is, itis a D.C. current), the flow of current in the secondary winding 34 willdiscontinue almost immediately.

If the fault sensing switch 39c is opened by a correction in theoperation condition of the equipment to which it is responsive, theaudible signal 28 will continue to be actuated until the acknowledgmentswitch 22 is opened to break the self-holding circuit of the relay. Onthe other hand, the usual situation is for the fault svw'tch 396 toremain closed, and the audible alarm 28 is deactuated by depressing theacknowledgment switch 22; and when the faulty condition in the equipmentassociated with the switch 390 is corrected, it will be opened and thelight 380 deenergized. In the meantime, however, should a condition ofabnormality be detected by another of the sensing switches, 39b forexample, it will close, the light 38b will be energized, and a currentHow of greater magnitude will be initiated through the secondary winding36 of the transformer because of the parallelism of the resistancesdefined by the two energized lights 38b and 380. This increase incurrent through the primary winding will establish a transient currentflow through the secondary winding 34 of the transformer, whereupon thetransistor will conduct and the relay 14 will again be energized toactuate the audible alarm 28. The acknowledgment switch 22 may again beopened to deenergize the relay and terminate the audible alarm, and thecircuit is again in condition for both visually and audibly indicating asubsequent abnormality at another detecting station.

The relay 14 will not be energized when the switches 39b and 39c areopened, for the resultant fiuX change in the transformer 35 will attemptto cause a current flow in the opposite directionthat is, from theemitter 30 to the base 29 in the transistor; and the current flow inthis direction cannot be accommodated thereby because of theuni-directional current flow characteristics thereof. Thus, while aninduced voltage in the secondary winding 34 of the transformer resultingfrom a current pulse through the primary winding thereof will energizethe relay 14 when a fault sensing switch is closed, the induced voltageof opposite polarity in the secondary winding will not energize therelay when one of the fault sensing switches is thereafter opened.

While in the foregoing specification an embodiment of the invention hasbeen set forth in considerable de tail for purposes of making a completedisclosure, it will be apparent to those skilled in the art thatnumerous changes may be made in those details without departing from thespirit or principles of the invention.

I claim:

1. In a fault annunciator system of the character described, a directcurrent power source, a relay having an energizing coil connected acrosssaid power source and being equipped with a pair of normally open switchcontacts, one of said contacts being connected in series with theenergizing coil to define a self holding circuit for said relay, a firstsignal device connected across said power source in series with theother of said switch contacts so as to be actuated when the relay isenergized, a transistor having a collector and emitter connected inseries with said energizing coil in shunt relation with said firstswitch contact, a transformer having a primary Winding connected acrosssaid power source and a secondary winding connected between the powersource and base of said transistor, a plurality of visual signal devicesand normally open fault switches, a visual signal device and faultswitch being connected in series, all of the visual signal device andfault switch combinations being connected in parallel with each otherand in series with said primary winding, any one of said fault switchesbeing adapted to be closed by a change in condition at a detectingstation to illuminate its associated visual signal device and inducevoltage in said primary and secondary windings to drive said transistorto conductive state to energize said relay, an acknowledgement switchconnected in series with said one switch contact and actuatable tode-energize said relay and said first signal device, the illuminatedvisual signal device remaining closed and said other fault switchesbeing actuatable to render said transistor conductive and re-energizesaid first signal dc VlCe.

2. In a fault annunciator system of the character described, a powersource, a relay having an energizing coil connected across said powersource and being equipped with a pair of normally open switch contacts,one of said contacts being connected in series with the energizing coilto define a self holding circuit for said relay, a first signal deviceconnected across said power source in series with the other of saidswitch contacts so as to be actuated when the relay is energized, aunidirectional impedance device connected in circuit with saidenergizing coil and in shunt relation with said first switch contact, atransformer having a primary winding connected across said power sourceand a secondary winding connected in circuit with said impedance device,a plurality of visual signal devices and normally open fault switches, avisual signal device and fault switch being connected in series, all ofthe visual signal device and fault switch combinations being connectedin parallel with each other and in series with said primary winding, anyone of said fault switches being adapted to be closed by a change incondition at a detecting station to illuminate its associated visualsignal device and induce voltage in said primary and secondary windingsto drive said impedance device to conductive state to energize saidrelay, an acknowledgement switch connected in series With said oneswitch contact and actuatable to tie-energize said relay and said firstnamed signal device, the illuminated visual signal device remainingclosed, and said other fault switches being actuatable to render saidimpedance device conductive and to re-energize said first signal device.

References Cited in the file of this patent UNITED STATES PATENTS

